NEW YORK -- It's been a struggle this season for outfielder Junior Lake, who the Cubs are hoping can get back on track playing every day at Triple-A Iowa.

Lake was optioned to Iowa to make room on the 25-man roster for pitcher Dan Straily, who started Saturday against the Mets. The outfielder was batting .216 with 102 strikeouts in 98 games. He hit .114 in July.

"We'll try to get him back on his feet again," manager Rick Renteria said. "It's tough for me to have him here. The window right now is just right" for him to go to the Minors.

Lake was told he would be back with the big league team when rosters expand on Sept. 1.

"Any time you have someone who has been with you as long as he's been with us, and you send him down late, it's obviously disappointing," Renteria said, "but I think he understands he'll get some at-bats and he knows he'll be back."